Epiphan, Jean N.. Disturbance in the forest of Morristown National Historical Park: influence of gap size on tree regeneration. Retrieved from https://doi.org/doi:10.7282/t3-w1gp-fn22
DescriptionDisturbance gaps in forests stimulate tree regeneration, maintain biodiversity, and promote forest heterogeneity. In urbanized regions, long term forest sustainability is threatened by many ecological stressors, such as high deer pressure and invasive plant spread, which can affect regeneration capabilities in disturbance gaps. This study tested whether forest gaps promoted tree regeneration in comparison to the adjacent intact forests and if gap size was an influential factor in regeneration. This study was conducted across 54 natural disturbance gaps of different sizes in a 590-ha forest tract within an urbanized region in Northern New Jersey. In each gap area, advanced regeneration data and species cover were collected in the understory stratum across three gap locations (gap center, gap edge, and adjacent forest). Results showed that advanced regeneration was greater in adjacent forest than in gap centers. Small Fraxinus spp. seedling numbers accounted for the difference among locations; when Fraxinus spp. were excluded there was no significance difference among locations. Gap size had no effect on advance regeneration. Overall, mean stocking index were severely deficient and mainly due to excessive deer pressure; numbers of large seedlings and saplings were severely low while numbers of all smaller seedlings were sufficiently stocked. In addition, invasive plants dominated the understory and stepwise multiple regressions showed that introduced shrubs and the introduced grass, Microstegium vimineum, displaced native tree regeneration. The only tree species that showed successful regeneration in gap centers was the introduced Robinia pseudoacacia which also had the greatest sapling numbers of all tree species. Without intervention, natural disturbance gaps in this stressed forest tract will fail to promote native tree regeneration, allow R. pseudoacacia to dominate, and change the future composition and structure of the forest. This study serves an example for the many forest tracts that bear similar ecological burdens. Intensive deer control and invasive plant management are required to restore natural regeneration processes and the valuable role of disturbance gaps to promote forest sustainability and heterogeneity.